Synergistic mixtures of selected amino acids

ABSTRACT

Novel synergistic fungicidal compositions used for protecting seeds, plants and other vegetative material against fungi contain a mixture of one or more compounds selected from group A and one or more compounds selected from group B. Compounds from group A are selected from β-Amino butyric acid and its N-benzoyl-octyl ester derivatives. Compounds from group B are selected from the group of fosetyl aluminum, dimethomorph, a mixture of folpet and ofurace (45:5), folpet, fencaramid (Bayer SZX), mancozeb, cymoxanil, methalaxyl, the single optical isomer of metalaxyl, a mixture of cymoxamil and mancozeb (4:1), copper sulfate, copper hydroxide, copper sulfate hydrate, azoxystrobin, and acibenzolar-s-methyl.

INTRODUCTION

[0001] The present invention concerns synergistic fungicidal mixtures. The present invention more particularly concerns synergistic mixture of β-aminobutyric acid (hereinafter referred to as BABA) and its N-benzoyl-octyl ester derivatives for the control of plant diseases.

BACKGROUND OF THE INVENTION

[0002] Fungicides are often combined in mixtures for 3 main reasons: 1. to widen the spectrum of antifungal activity to control several diseases occurring simultaneously in a crop 2. to exploit synergistic interaction between fungicides, by which the overall activity is increased and the concentration of the compounds reduced, and 3. to delay the selection process of resistant fungal individuals to one compound of the mixture (Gisi, Phytopathology 86 1273-1279, 1996).

[0003] Avoidance of plant disease in agricultural production may be accomplished not only by using fungicides or fungicidal mixtures but also by using “plant activators”, molecules which enhance the natural resistance (defense) of the plant. Such activators which have no direct fungicidal effect on the pathogen (Ryals et al The Plant Cell: 1809-1819, 1996), induce systemic acquired resistance (SAR) in the plant several days after application (Ibid).

[0004] To date only few molecules were reported to induce SAR in crop plants viz. salicylic acid (SA), 2,6-dichloroisonicotinic acid (INA) benzol (1,2,3)thiadiazole-7-carbothiouic acid S-methyl ester (BTH) (Ibid), and DL-3-amino butyric acid (BABA, Cohen et al Plant Physiology 104: 56-59, 1994).

[0005] However whereas SA, INA or BTH have to be applied to the crop ahead of infestation (Ryals, et al Ibid) BABA can be applied post-inflectionally (Cohen et al Ibid).

[0006] The idea behind the present invention is to combine two methods of disease control—the direct-kill method operating on the target pathogen and the indirect method of activating the natural defense approach of the crop plant. Such two methods are combined by using mixtures of a fungicide or fungicides (direct-kill) with BABA or its N-benzoly-octyl ester derivative (SAR).

[0007] We show here that such mixtures are synergistic in controlling plant diseases.

OBJECTIVES OF THE INVENTION

[0008] It is the objective of the present invention to provide novel mixtures of fungicides of β-aminobutyric acids. It is an objective of the present invention to provide a synergistic mixture of BABA and/or its N-benzoyl-octyl ester derivative with various other fungicides.

SUMMARY OF THE INVENTION

[0009] In accordance with the present invention there is provided synergistic fungicidal composition comprising one or more compounds selected from Group A and one or more compounds selected from Group B; wherein the compounds of Group A are selected from the group consisting of DL-3 aminobutyric acid and its N-Benzoyl octyl ester, and the compounds of Group B are selected from the group consisting of fosetyl aluminum, dimethomorph, a mixture of folpet and ofurace ((45:5), folpet, fencaramid (Bayer SZX), mancozeb, cymoxanil, methalaxyl, the single optical isomer of metalaxyl, a mixture of cymoxamil and mancozeb (4:1), copper sulfate, copper hydroxide, copper sulfate hydrate, azoxystrobin, and acibenzolar-s-methyl.

[0010] The present invention also provides an improved method of controlling fungi, especially late blight and downy mildews, applying to the plant a composition containing an effective amount of one of these mixtures. The present invention further provides an improved method of controlling phytophthora infertan in potato or tomato, Pseudoperonospora cubensis in cucumber or melon, Plasmopera viticola in grapes, and Peronospora tabacina in tobacco.

DETAILED DESCRIPTION OF THE INVENTION Methodology

[0011] Plants

[0012] 1. Potato (cultivar Alpha) were grown from tubers in 1 liter ports in sandy oil in the greenhouse. At 5 weeks after planting when they had several shoots in a pot, with 10-12 leaves per shoot, plants were taken for assays.

[0013] 2. Cucumber (cultivate Dlila) plants were grown from seed in 0.251 liter pots containing sandy soil in the greenhouse. At 3 weeks after sowing, when they developed 2 leaves they were used.

[0014] 3 Grapes (cultivate Superior) plants were grown from cuttings (first in perlite and then in sandy soil) in pots in the greenhouse. At 8 weeks after planting leaves were detached for experiments.

[0015] Fungal Pathogens.

[0016] Potatoes were inoculated with sporangic of Phytophthora infestans (resistant to metalaxyl). Cucumbers were inoculated with sporangia of Pseudoperonospora cubensis (resistance to metalaxyl). Grapes were inoculated with Plasmopara viticola

[0017] Chemicals.

[0018] 1. DLβ-amino-butanoic acid (BABA)

[0019] 2. DL-4-benzoyl-3-amino butanoic acid octylester (039-81)

[0020] 3. Cymoxanil (Curzate)

[0021] 4. phosetyl aluminium (Alliette)

[0022] 5. Mancozeb

[0023] 6. Folpet

[0024] 7. Metalaxyl, metalaxyl-Gold

[0025] 8. Copper sulphate, copper hydroxide

[0026] 9. (Mancozeb+dimethomorph, prepacked 600 g±90 g a.i. per 1 kg)

[0027] 10. (Mancozeb+metalaxyl, prepacked 560 g+75 g a.i. per 1 kg)

[0028] 11. Folpet+ofurace, 450 g+60 g a.i. per 1 kg)

[0029] 12. Bayer-SZX (Fencaramid)

[0030] 13. Mancozeb+Cymoxanil (4:1)

[0031] 14. Azoxystrobin

[0032] 15. Acibenzolar-s-methyl

[0033] 16. Dimethomorph

[0034] Except BABA which was dissolved in water, all other chemicals or prepacked mixtures produced a suspension or emulsion in water.

[0035] Spraying

[0036] The chemicals were sprayed onto the upper leaf surfaces of either potatoes or cucumbers with the aid of a fine glass atomizer. Control plants were sprayed with water. Experiments with grapes were carried out using 12 mm leaf discs floating on 1 ml of the test compound(s) in 24-well titer plants, upperside down.

Inoculation

[0037] Potatoes and cucumbers were inoculated one day after spraying. Grape leaf disc were inoculated soon after floating

[0038] Inoculation of potato was done by spraying the upper leaf surfaces of the plants with a sporangial suspension containing 2000 sporangia/ml. Sporangia were harvested 0.5 h before inoculation from infected potato tuber slices. Cucumbers were sprayed with a sporangial suspension containing 1500 sporangia/ml. Sporangia were harvested from infected cucumber plants kept in humid growth chambers (at 15° C.). Leaf discs of grapes were inoculated with 2 sporangial droplets containing each 300 sporangia. Sporangia were harvested from infected leaves kept in petri dishes on wet filter paper at 15° C. Inoculated plants or titer plates were placed in a dew chamber at 18° C. overnight and then transferred to a growth chamber at 20° C. (12 h light/day 100 pE.m⁻².S⁻¹) for symptom production (late blight in potato and downy mildew in cucumber), or for sporulation of P. viticola in grape leaf discs.

General Procedure for Tobacco

[0039] One month old tobacco plants (cv. xanthi nc.) were sprayed onto their foliage with the test compounds. Two days later they were inoculated with 10⁴ spores/ml of Perouospora latacin of either the S or the R strain. Inoculated plants were placed in 100% relative humidity overnight and then incubated at 20° C. with 12 h light/day. A week after inoculation plants were again placed at 100%-RH at 18° C. in the dark to induce fungal sporulation. Sporulation was quantitated by removing 2 cm² leaf discs from each leaf and counting with the aid of a haemocytometer. The extent of sporulation inhibition was calculated relative to that in control (untreated) inoculated plants. ED_(go) was computed after linear regression and was calculated according to Wadely.

General Procedure for Grapes

[0040] Leaf discs (2-cm²) were removed from the top leaves of grape plants (cv. Superior) grown in the greenhouse. Discs were floated (lower surface uppermost on the test solution over filter paper of 9 cm diameter). Petri dishes. Leaf discs were immediately inoculated with 2 (10 ml) droplets of sporangial suspension (10⁴/ml) of Plasmopara viticola per disc. Dishes were incubated at 20° C. with 12 h light/day for 10 days until fungal sporulation was quantified.

Disease Assessment

[0041] At the time intervals post inoculation specified in the Examples, infected leaf area in potato and cucumber was assessed visually. In control inoculated plants most or all of the foliage (80-100%) was devastated by the disease. Percentage control of the disease by a chemical treatment was calculated as

% control=(1−x/y)×100

[0042] whereas

[0043] x=proportion leaf are diseased in treated plants and

[0044] y=proportion leaf area diseased in control plants.

[0045] In grapes, proportion of leaf discs showing sporulation were similarly used.

Calculation of Control Efficacy and Synergism

[0046] Each chemical and each mixture was applied to plants at various doses of the active ingredient. Dose-response curves were produced and transferred to log-dose probit response curves as described by Kosman and Cohen (Phytopatholagy 86: 1263.1272, 1996). ED₉₀ values (dose required for achieving 90% control of the disease) taken from the log-probit 7 curves were used to calculate the Cotoxicity Factor (CF) according to the Wadely procedure (Kosman and Cohen, Ibid; Gisi phytopatcology 86: 1273-1279, 1966). “CF’ is defined as the ratio between the expected dose and the observed dose that provide the same level of disease control (Kosman and Cohen, Ibid). The observed dose of each component of a mixture is taken from the experiment and the expected dose of all mixture made of those components is calculated by the Wadely formula: ${{ED}_{90}\quad \text{expected}} = \frac{a + b}{\frac{a}{{ED}_{90}\quad {{obs}.A}} + \frac{b}{{ED}_{90}\quad {{obs}.B}}}$

[0047] where a and b are the absolute amounts of the components A and B in a mixture and ED₉₀ obs.A and ED₉₀ obs.B are then ED₉₀ values of A and B obtained by the experiment. CF values of >2.0 are considered to represent a strongly synergistic mixture (Gisi, Ibid). According to a further feature of the invention, there is provided a fungicidal composition which comprises a compound of the invention together with carrier. The active compound can be employed as a wide variety of formulations, for example as an aqueous dispersion, a dispersible powder, as seed dressing, granules or dust. As a dispersion the composition comprises an active compound together with a dispersing agent dispersed in a liquid medium, preferably water. It can be in a form of a concentrated primary composition which requires dilution with a suitable quantity of water or other diluent before application. Such primary compositions are a convenient way of supplying the consumer and preferred example is a dispersible powder. A dispersible, powder comprises an active compound, a dispersing agent and solid carrier. The latter can be, for example, kaolin, talc, or diatomaceous earth and in addition, the dispersible powder can contain a wetting agent.

[0048] Other formulations include seed dressing, granules or dusts, in all of which the active compound is associated with a solid carrier and which are intended for direct application. They can be made by methods well known in the art. Preferably all compositions comprising a solid carrier are made by mixing the active compound in particulate form with a particulate carrier.

[0049] The concentration of the active compound in the composition of the invention can vary widely. In the case of a primary composition it is preferably from 15% to 95% by weight, more especially from 50% to 80% by weight. A composition intended for direct application to a crop preferably comprises from 0.001% to 10% more, especially from 0.005% to 5% by weight of the active compound, although the aerial spraying of a crop is contemplated compositions having higher concentrations, for example up to 30% by weight may be chosen in preference.

[0050] The fungicidal composition of the present invention may be applied as a ready-mixed composition, as a tank mix, or applying the compounds of each group separately.

[0051] Following the methods outlined above numerous mixtures were prepared and their activity against a variety of diseases was studied. The results of 35 studies are listed in Tables 1-35

[0052] While the invention will now be described in connection with certain preferred embodiments in the following examples it will be understood that it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as be included within the scope of the invention, as defined by the appended claims. Thus, the following examples which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purposes of illustrative discussion of preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of procedures as well as of the principles and conceptual aspects of the invention. 

What is claimed is:
 1. A synergistic fungicidal composition comprising synergistically effective respective amounts of (1) D,L-3-aminobutyric acid or the n-octyl ester thereof, together with (2) azoxystrobin.
 2. The fungicidal composition of claim 1, wherein the (1) D,L-3-aminobutyric acid or n-octyl ester thereof and the (2) azoxystrobin are present in a weight ratio of 9:1 to 1:9.
 3. The fungicidal composition of claim 2 wherein said weight ratio is 4:1 to 1:4.
 4. The fungicidal composition of claim 1 wherein fungicidal components consist essentially of said (1) D,L-3-aminobutyric acid or n-octyl ester thereof and (2) said azoxystrobin.
 5. A method of administering a fungicidal composition in accordance with claim 1 to a plant infested with a fungus, wherein the fungus is selected from the group consisting of Phytophthora infestans, Pseudopersonspora Cubensis, Plasmopara veticola, and Peronospora tabacina.
 6. The method of claim 5 wherein the fungus is selected from the group consisting of Phytophthora infestans in potatoes and tomatoes, Pseudoperonspora Cubensis in cucumber and melons, Plasmopara veticola in grapes, and Peronospora tabacina in tobacco.
 7. A method of controlling fungal infections in plants comprising applying to the plants or parts thereof a synergistic fungicidal composition comprising synergistically effective respective amounts of (1) D,L-3-aminobutyric acid or the n-octyl ester thereof, and (2) azoxystrobin.
 8. The method of claim 7 which comprises applying (1) said D,L-3-aminobutyric acid or n-octyl ester thereof and (2) said azoxystrobin in a weight ratio of 9:1 to 1:9.
 9. The method of claim 8 wherein said weight ratio is 4:1 to 1:4.
 10. The method of claim 7 wherein the plants are selected from the group consisting of potatoes, tomatoes, cucumbers, melons, grape vines and tobacco.
 11. A method according to claim 7 wherein the fungus is selected from the group consisting of Phytophthora infestans, Pseudopersonspora Cubensis, Plasmopara veticola, and Peronospora tabacina.
 12. A method in accordance with claim 10 wherein the fungus is selected from the group consisting of Phytophthora infestans in potatoes and tomatoes, Pseudopersonspora Cubensis in cucumber and melons, Plasmopara veticola in grapes, and Peronospora tabacina in tobacco. 